cleanup: differentiate logger tags — 'core' used by 5+ unrelated modules

[SisyphusZheng]

Problem

createLogger('core') is used by 5+ modules with unrelated responsibilities:

Module	Actual responsibility
packages/element/src/internal/core/island.ts	Island registration
packages/element/src/internal/core/render-dsd.ts	DSD rendering
packages/adapter-vite/src/internal/ssg/route-scanner.ts	Route scanning
packages/adapter-vite/src/internal/ssg/postprocess.ts	Build post-processing
packages/adapter-vite/src/internal/ssg/build-postprocess.ts	Build post-processing
packages/adapter-vite/src/internal/ssg/island-scanner.ts	Island scanning

All emit [core] ... making it impossible to identify the source in build logs or browser console.

Fix

Assign specific tags per module:

Module	New tag
island.ts	'island'
render-dsd.ts	'render-dsd'
route-scanner.ts	'scanner'
postprocess.ts	'postprocess'
build-postprocess.ts	'postprocess'
island-scanner.ts	'island-scan'

Keep 'core' reserved for truly core-level messages only (e.g., errors.ts).

Acceptance

• No more than 2 modules share the same logger tag
• Build output logs are distinguishable by source module